Experimental Investigation On The Discharge Characteristics Of A Linear-field Brush-shaped Argon Plume With Two Kind Of Excitation

Using a plasma jet composed of line to plate electrodes, a brush-shaped Argon plasma plume is generated in the air through a direct current voltage or an alternating current voltage excitation. The discharge characteristics of the both brush-shaped plasma plumes excited by a direct current voltage and an alternating current voltage are investigated.Under the direct current voltage excitation, the length of the plasma plume increases a little with increasing the gas flow rate and the output power. By spatially resolved measurement of emission intensity (Ar,763.5 nm) and the emission profiles are obtained. It can be found that the emission signal near the two edges of the linear electrode is stronger than the middle of the linear electrode, and profile near the outlet is symmetric. The peak near the linear electrode is greater than that near the plate electrode. At anywhere of the discharge, the electron excitation temperature increases with the increases of the gas flow rate or the applied voltage, and the molecular vibrational temperature increases with the increases of the applied voltage, and decreases with the gas flow rate. The discharge current and the total light emission of the plasma plume show a pulsed characteristic. The pulse frequency keeps constant with increasing the gas flow rate, and it increases with increasing the applied voltage. Based on the voltage-light emission curve, the brush-shaped plume is in fact an overlaps of the plasma bullet, and it appeared at different place of the linear electrode and moving to the plate electrode. We are also calculate the speed of the plasma bullet, it's about several hundreds kilometer per second.Under the alternating current voltage excitation, without ballast resistor, a brush-shaped air plasma plume with relatively large volume is generated. The brightness and the uniformity of the plasma plume increases with increasing the averaged peak voltage. The number of light emission pulse of the positive half cycle of applied voltage is on the increase with the increase of the applied voltage, but unchanged of the negative half cycle of applied voltage. The plasma parameters such as the electron excitation temperature, the vibrational temperature are change with the applied voltage, the emission intensity of 337.lnm and 763.5 nm along the linear electrode and the gas flow are investigated based on the optical spectrum emitted from the laminar plume. The optical fiber thermometer is for measuring gas temperature, from the result, the gas temperature is sensitive to both of the gas flow rate and the applied voltage. Based on high-speed photography by the scale of nanosecond exposure time, the brush-shaped plume is in fact a temporal overlaps of the plasma bullet (different place at linear electrode) at the positive half cycle of the applied voltage. But for the negative half cycle of the applied voltage is a funnel-shaped luminous layer, it can be deduced that the discharge of the negative half cycle of the applied voltage is remains dominated by a Townsend discharge mechanism and the funnel-shaped luminous layer just appears between the linear electrode and the outlet. Using the optical method to measure the Spatial-resolved of the light emission pulse of the plasma plume, the result is consistent with the snapshots, and the existence of the plasma bullet is explained from the discharge characteristic. Increasing the applied voltage, the ICCD has taken more than one plasma bullet at same time, that mean the plasma bullet is appeared at different place of the linear. We have statistics the position of the plasma bullets and the position of the streamer layer. The results are consistent with the macroscopic discharge images.